You seem to be equating the success of bitcoin with the number of human beings using mining equipment. I'd say there's an optimal number somewhere, maybe a few thousand people, that are needed to keep the diversity of mining healthy. Too few people and you risk one set of problems. Too many people and you have another set of problems. But the primary reason for mining is to secure the network. ASICs will bring much increased security to the blockchain, as long as there's enough of them. And by all accounts, there are plenty of people pre-ordering ASICs, so there's nothing to worry about. Not everyone that uses bitcoin needs to be a miner. In fact, we don't want everyone to be a miner. There is much overhead with being a miner. It's not appropriate for everyone.